Field of Invention
The present invention belongs to the field of sealing testing technology, and more particularly relates to a device for testing mechanical seal performance which has no additional axial force and is capable of accurately testing the torque. The device is adapted for testing mechanical seal performance of the rotating machinery with large diameter including large compressors and centrifugal pumps for conveying high pressure media, or stirred tank reactors for mixing high pressure media.
Description of Related Arts
It is required of mechanical seals with stable performance to meet the demand of large-scale, integration, and long-term operation of the production device. Therefore, device for testing mechanical seal performance with broad operating parameters and convenient test are needed to be designed to adapted for the development and testing of new mechanical seals.
It can be seen from the widely-known technology, the support structure of the main shaft of the device for testing mechanical seal performance is in forms of single cantilever shaft, double cantilever shafts and double support shafts. The main shaft inserts into the end cover at the single side or into the end covers at two sides and out of the working chamber. For the single cantilever shaft type device for testing mechanical seal performance, the main shaft inserts into one end cover of the working chamber, the mechanical seal to be tested is used as a sealing member of the working chamber, such as Patent ZL 00220907.1. However, the shaft ends of the main shaft situates in the medium of the working chamber, generating a larger axial force, and simultaneously, the areas of the rotating rings and the stationary rings of the mechanical seal to be tested bear the action from the medium are different, which also generates the axial force. Large axial force is harmful to the service life of the bearing. Different axial forces lead to different bearing resistance torque, finally the measurement accuracy of the end-face friction torque is affected. For the device with the single cantilever and main shaft passing into and outside end covers at two sides of the working chamber for testing mechanical seal performance, the axial force of the medium in the working chamber at the shaft ends is avoided, two groups of mechanical seals to be tested with a same regulation and size are symmetrically distributed within the working chamber; the shaft sleeve has two segments of thread at one end , the two segments of thread have the same screw pitch and opposite rotation directions; the shaft sleeve is rotated to drive the left and right nuts which are screwed and jointed with the shaft sleeve to move left and right equidistantly, so as to drive the left and right rotating ring seats to tightly press two rotating rings via the springs, for achieving equally loading the end-face specific pressure, such as Patent CN201210037262.6. However, it is very difficult for the two groups of mechanical seals to be symmetrical with the center cross section of the working chamber at the initial position. For double cantilever type device for testing mechanical seal performance, such as Patent ZL88214684.X, the axial force caused by the medium pressure at the single shaft end, and the axial force due to different areas of the rotating and stationary rings of the mechanical seal to be tested bear the medium force, are balanced via the symmetrically whole structure. However, the main shaft and the driving connecting structure are still complex. For double support shafts type device for testing mechanical seal performance, such as Patent CN201210126379.1, the main shaft inserts into and out of the end covers at two ends of the working chamber, two groups of mechanical seal to be tested with a same regulation and size are symmetrically arranged within the working chamber to resolve the balance problem of the axial force and the effect of the winding degree of the cantilever shaft. However, it is very inconvenient for installing the mechanical seal to be tested, and especially it is very difficult to meet the requirements of quick assembly and disassembly during type experiments.
The above existing technologies, while experimenting, the torque sensor tests the total torque on the main shaft in the experimenting device, the total torque includes the friction torque of the sealing end face to be tested and the friction torque of the bearing of the main shaft. The friction torque of the sealing end face to be tested equals to the total torque minus the friction torque of the bearing of the main shaft measured before experiment. Therefore, not only the experimental process is complex, but also the accuracy of the test is reduced.
Furthermore, in the above existing technologies, the torque tests the total torque on the main shaft of the experimental device. However, while starting, the staring torque is 5-7 times that of normal operation. Therefore, the diameter of the stress shaft of the torque sensor is larger. The torque sensor is used to test the smaller end-face friction torque of mechanical seal at the normal operation state, the generated axial stress is smaller, the measurement accuracy is lower. To improve the measurement accuracy, the diameter of the stress shaft of the torque sensor should be reduced. However, it is easy for the stress shaft with smaller diameter to generate plastic deformation, even fracture. Therefore, two aspects are mutually exclusive.